The ornamental design for an H-shape upright glazing pane support with unconnected top flanges for window sash, as shown and described.
FIG. 1 is a front end elevational view showing the design, the rear end being a mirror image thereof, with broken lines depicting an example sash profile environment related to the design for illustrative purposes only and forming no part of the claimed design; and,
FIG. 2 is a front perspective view showing the design, with broken lines depicting an example sash profile environment related to the design for illustrative purposes only and forming no part of the claimed design, and is shown fragmented indicating indefinite length.